An image forming device is known which forms an image on a recording medium by transferring transfer materials respectively for a plurality of transfer material areas repeatedly arranged in the longitudinal direction of a strip-shaped transfer medium. Specifically, an image forming device is known which partially uses the transfer material areas to form an image having a size not more than one-half of a transfer material area, and thereafter rewinds the transfer medium, and then uses unused portions of the partially used transfer material areas to form a new image having the same size.
Patent Literature 1 describes a thermal transfer color printer which uses, when performing L-size printing by using an ink ribbon corresponding to 2L-size, the rear part of each ink area of the ink ribbon (rewinding direction of the ink ribbon) prior to the front part (winding direction of the ink ribbon) thereof which is normally considered to be used prior to the rear part. With this printer, if L-size printing is performed in two steps, when the ink ribbon which has been used to print the first sheet is rewound and reused, the second sheet can be printed without being affected by creases formed in the portion of the ink ribbon where the ink has been exhausted.
Patent Literature 2 describes a thermal transfer recording device for transfer-recording an image on a recording sheet by using an ink sheet corresponding to an A4 size recording sheet and including dye portions for different colors. This thermal transfer recording device includes a counter to count the number of recorded sheets up to the present time in an A5 size recording mode, and in the case of a continual recording on a A5 size recording sheet, when the number of the sheets counted by the counter is an odd number, the transfer recording of each color is conducted in the same way as A4 size recording, and when the number of the sheets counted by the counter is an even number, the transfer recording of each color is conducted while the ink sheet is rewound by driving a rewinding motor.
Patent Literature 3 describes a transfer method in a recording device which superimposes and transfers different color inks onto a recording sheet from an ink sheet having a plurality of color inks successively applied thereon in the feeding direction. With this transfer method, if an image is transferred onto a recording sheet whose surface area is approximately one-half of each surface area of the ink sheet that has been coated with an ink, front halves of respective color ink-applied areas are used to transfer an image, thereafter, the ink sheet is rewound to a portion where the rear halves of the ink-applied areas can be transferred, and another image is transferred by using the rear halves of the ink sheet.
A transfer medium provided with a marking such as a black borderline which is used to detect a border between transfer material areas is known. However, transfer media without such markings are more commonly used, in order to provide as large transfer material areas as possible. In response to such transfer media, an image forming device is provided with a detection unit which detects the border between the transfer material areas based on a change of the colors of the transfer material areas that are fed and pass the detection position.